As known, electrical apparatuses for the control and/or distribution of electric power, such as for example circuit breakers, comprise a box-shaped body made from electrically insulating material having a bottom wall and side walls delimiting an inner space for housing electromechanical mechanisms of the electrical apparatus. At a front face of the box-shaped body a manual actuation device is generally provided, such as for example a lever, a rocker arm or a button. In some of the aforementioned electrical apparatuses the bottom wall of the box-shaped body is equipped with an access opening to the inner space intended for being traversed by a fitting device, like for example an LED backlighting device, which can be operatively coupled to the electrical apparatus. In some of the electrical apparatuses of the prior art the access opening is already foreseen and left open during the manufacturing of the electrical apparatus. The access opening represents an area of undesired intrusion of dust and similar particles, such as for example grains of sand and particles of construction material, inside the box-shaped body.
In order to reduce the aforementioned drawback given by the undesired intrusion of dust and similar through the access opening, in some electrical apparatuses the access opening is practically obtained only during installation of the electrical apparatus, since the opening is initially occluded by a removable closing wall generally at least partially delimited and surrounded by pre-fractures/weakenings foreseen so as to facilitate its removal. The removal operation of the closing wall complicates the installation operations, moreover there is the risk that during the removal operation the closing wall itself or undesired particles that temporarily stick to the tool used for the removal fall back inside the housing space through the access opening thus nullifying the function of the removable closing wall.
The undesired intrusion of dust or particles in electrical apparatuses as described in patent applications WO 2006/106554 and WO 2010/0006867 is particularly problematic since it can determine jamming of the control mechanism. In other types of electrical apparatuses such an undesired intrusion is in any case problematic since the dust or the particles can contaminate the electromechanical or electrical components housed inside the housing space, causing faults, a degradation of performance or temporary malfunctioning.
Patent application WO 2007/043882 describes an electrical apparatus comprising a protective device comprising a tearable membrane. It is considered that such a membrane is ineffective in the case in which in the body of the apparatus further openings are foreseen, with respect to the one occluded by the membrane itself, suitable for allowing access to the connection terminals in the form of screw clamps. Moreover, the aforementioned tearable membrane potentially has the drawback of producing, in the tearing operation, fragments that can contaminate the inner space of the electrical apparatus.
It is felt necessary to have an apparatus available that is improved in relation to at least one or two aforementioned drawbacks with reference to patent application WO 2007/043882.